Please bear with me as I explain my problem. I think I have a basic understanding of how the technology works, but I am not conversant enough in the technical language to describe it properly.

My home office is in an addition to our house. The original outside wall is still there. Something about that wall causes a great deal of interference with wireless devices unless the wireless device is in a straight line of sight through the doorway. I have the cable company's modem/adapter hooked to a cordless phone base with multiple handsets (5.8ghz) and to a wireless router in my home office. I have set up a wireless network access point in the center of my home in sight of the the wireless router. The wireless access point works fine to connect the iMac, PCs and networked TIVOs to the broadband service. I used Belkin wireless 54g network stuff for all of that. Unfortunately, the cordless handsets will not work unless they are within the line of sight of the base.

Right now, I have Voip phone service through my local cable company. It was set up to work through the existing phone wires in my house. We had a recent water problem and my phone wiring no longer works. Repairing that wiring will cost us between $250 and $500. I was planning to switch to Vonage before the phone wiring was damaged since it less expensive and more versatile than the service I have from local cable company. However, not being able to use the existing phone wires kind of throws a big wrench into that plan. It seems theoretically possible for me to purchase some additional equipment to work with Vonage and my existing wireless network for much less that it would cost to replace the existing phone wiring. However, if that isn't the case, and I must get the wiring fixed, we may need to investigate other options.

Okay, here's the question part --

Assume that I switch to a different modem (I have a Motorola SB5120 that we used before we got the one from the cable company) and get Vonage service. Will connecting a phone adapter like the D-Link VTA to my my wireless access point via the LAN connection on said wireless access point and then connecting my cordless phone base to the phone adapter (in a place that will allow my cordless handsets to reach the base from anywhere in the house without the interference caused by that wall) actually work with the Vonage service?

Yes it will work. Plugging in the main base phone into the a Vonage phone adapter will give phone service to the remaining phone handsets. The only negative is that the main base station will need to be near the phone adapter unless you don't mind a long phone line running between the phone adapter and your base phone.

What you want to do will work, as Taylor said. However, it does require that your wireless router and access point both work very well, even if someone should be walking through the door to your office while you're on the phone.

You might also consider the possibility of partially using the house wiring if some of it wasn't damaged. If you have a phone jack in your office and another on the other side of the evil wall, and if there is just one good pair between them, you could cut everything else loose. Then set up the adapter in the office, use a corded phone there, and use that one wire run to get to the cordless base outside the wall.